Gripping unit for automated machining of parts, and machining device and process integrating such a unit

ABSTRACT

Gripping unit for automated machining of parts and device and process integrating such a unit.  
     The gripping unit comprises a pallet ( 16 ) that supports gripping systems ( 18 ) through orientation systems ( 22 ). The pallet ( 16 ) also supports at least one control box ( 28 ) capable of activating orientation systems ( 22 ), and possibly gripping systems ( 18 ) to modify the position or orientation of the block of material to be machined when the gripping unit is placed in a machine tool ( 12 ). The control system ( 28 ) takes actions in response to orders issued by the control system ( 40 ) of the machine tool ( 12 ).

DESCRIPTION

[0001] 1. Technical Domain

[0002] The main purpose of the invention is a gripping unit used totransfer a mechanical part to be machined between at least one machinetool and at least one loading unloading station, to enable automatedmachining of the said part on each of its faces without the need foraction by an operator during the machining.

[0003] The invention also relates to a machining device integrating atleast one gripping unit of this type, at least one machining machine andat least one loading unloading station.

[0004] The invention also relates to a machining process that could beused by such a device.

[0005] 2. State of the Art

[0006] Normally, when a part has to be machined in a machine tool, anoperator can put it into position in a specific gripping tool, directlyfixed onto the plate of the machine tool. A relative long stoppage ofthe machine is necessary to put the tooling into place and to adjust it,which reduces productivity. This productivity reduction is particularlysevere because the part usually needs to be turned over to be able tomachine all the faces of the part. Furthermore, when the part is beingturned over, the gripping tool sometimes needs to be replaced by anothertool better adapted to the new orientation of the part.

[0007] Document FR-A-2 691 659 describes a gripping tool with a modulardesign, used to put the part into place and to adjust the orientationoutside the machine tool, for example at a loading station. The grippingtool comprises a sole plate, in other words a pallet composed of arectangular plate designed to be fixed on the plate of the machine tool.A vertical body fixed to this pallet can be fitted with at least onegripping module. This gripping module is chosen from among differentmodules (vices, grips, etc.), that can be interchanged with each otherdepending on the part to be machined.

[0008] The part to be machined is put into place on the gripping modulein a loading station outside the machine. The operator selects thegripping module so as to clamp the part in the required position.Consequently, the loading station supplies hydraulic fluid to thegripping module under pressure. The gripping module comprises areservoir of pressurized hydraulic fluid to keep the part clamped inplace during the waiting and transfer phases between the loading stationand the machine tool.

[0009] The gripping tool proposed in document FR-A2 691 659 is used toput parts into position in advance, without requiring a long stoppage ofthe machine. However, when the part must be turned over to machine someof its faces, the gripping tool must be brought to the loading stationso that an operator can turn the part over, and if necessary replace thegripping module. This is penalizing in terms of productivity and themanufacturing time for the part. The machine tool is stopped while thetooling is removed and put back into place. Furthermore, action by anoperator is necessary.

DESCRIPTION OF THE INVENTION

[0010] The main purpose of the invention is a gripping unit with aninnovative design such that all faces of a mechanical part can bemachined in an automated manner without the need for any action by anoperator or return to a loading station.

[0011] According to the invention, this objective is achieved by meansof a gripping unit that can be transferred between at least one machinetool and at least one loading unloading station, to enable automatedmachining of at least one part, the gripping unit comprising a palletand means of gripping the said part, mounted on the pallet, and beingcharacterized in that it also comprises orientation means used to mountthe gripping means on the pallet, control means capable of actuating theorientation means in response to control signals output from the machinetool, and bearing means installed on the pallet by other orientationmeans.

[0012] In this type of gripping unit, the instrumentation control devicein particular checks the position and movements of orientation means bywhich the gripping means are mounted on the pallet. This check is madelocally and independently, as a function of set points originating fromthe machine tool. Therefore, the part can be machined on each of itsfaces in sequence without it being necessary to return the gripping unitto the loading unloading station. Complete automated machining is thuspossible without increasing the workload carried out by the controldevice installed on the machine tool.

[0013] In one preferred embodiment of the invention, the control meansare also capable of actuating gripping means. Thus, the block ofmaterial to be machined can be clamped and the machined part can bedisassembled automatically at the loading unloading station.

[0014] According to this preferred embodiment, at least one frame isfixed on the pallet and a rotary plate is installed on the frame andforms the orientation means. The gripping means are then installed onthe rotary plate.

[0015] The support means preferably include at least one surface thatmight be applied on the part, the said surface being made of a materialthat absorbs vibrations. Furthermore, the other orientation meanscomprise another rotary arm installed on the pallet.

[0016] In the preferred embodiment of the invention, the gripping meansare interchangeable.

[0017] Advantageously, the pallet comprises a part free to move inrotation about an axis perpendicular to a face of the pallet with thelarger surface area, the gripping means being mounted on the said mobilepart. This arrangement gives an additional degree of orientation, whichin some cases facilitates machining of all faces of the block ofmaterial.

[0018] In one particular embodiment, the gripping unit also comprisesfirst connection means that can be automatically connected to the twoconnection means mounted on the machine tool when the modular unit isfitted into the machine tool.

[0019] Advantageously, the modular unit then includes third connectionmeans connected firstly to the first connection means and secondly tothe orientation means and control means.

[0020] In general, the control means are preferably connected to acommunication bus capable of transmitting the control signals. Thissolution has the advantage that it only requires the exchange of a verylimited number of signals between the control means and the machinetool. Advantageously, the communication bus then uses a wireless link.

[0021] In the preferred embodiment of the invention, the gripping unitalso comprises at least one onboard energy reserve. This energy reserveat least clamps the block of material to be machined in the grippingmeans, during transfers of the gripping unit between the loadingunloading station and the machine tool, when the said gripping meanshave to be permanently powered.

[0022] In this case, the energy reserve may be sized to supply thequantity of energy necessary for complete machining of an arbitrary parton the machine tool.

[0023] According to a preferred improvement of the invention, thegripping means may exert a tension force on the part, to modify itsnatural frequency and thus limit vibrations of the part duringmachining.

[0024] Preferably, vibration detection means are then installed on atleast one of the gripping means. Signals output by vibration detectionmeans are then advantageously transmitted to control means that regulatethe tension force exerted on the part, to minimize its vibrations.

[0025] Furthermore, the control means may be placed in at least oneairtight box that can protect them from any aggressions that may beapplied to them when the part is machined on the machine tool. Heatextraction means are then installed on the box if necessary.

[0026] Another purpose of the invention is a part machining device,comprising at least one gripping unit like that described above, atleast one machine-tool on which the gripping unit is held, at least oneloading unloading station in which then gripping unit will be held, andmeans capable of transporting energy to the gripping unit, in which eachmachine tool also comprises second control means capable of sending thesaid control signals, and signal transmission means are provided totransmit the said control signals between the control means for thegripping unit and the second control means, when the gripping unit isheld on the machine tool.

[0027] Another purpose of the invention is a process for machining partsusing a device like that described above, comprising the followingphases :

[0028] a design phase consisting of defining successive orientations ofa part in the machine tool and machining sequences specific to each ofthese orientations:

[0029] a manufacturing phase comprising the following steps :

[0030] placement of the gripping unit at the loading unloading station;

[0031] placement of gripping means on the gripping unit;

[0032] placement of a block of material to be machined on the grippingunit and clamping of the said block by the gripping means;

[0033] transfer and placement of the gripping unit on the machine tool;

[0034] orientation of the said block in a first of the predefinedorientations, when acted upon by orientation means controlled by thegripping unit control means at the request of the second control means;

[0035] execution of machining sequences corresponding to this firstposition;

[0036] repetition of the block orientation and machining sequenceexecution steps as many times as necessary, in accordance with thedesign phase, until the part is completed;

[0037] transfer of the gripping unit to the loading unloading station;

[0038] loosening and unloading the part.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] We will now describe the different embodiments of the inventionas illustrative and non-restrictive examples, with reference to theattached drawings in which:

[0040]FIG. 1 is a front view that diagrammatically shows a machiningdevice integrating a gripping unit conform with the invention;

[0041]FIG. 2 is a perspective view that shows a first embodiment of agripping unit conform with the invention, and gripping of a block ofmaterial to be machined, in more detail;

[0042]FIG. 3 is a perspective view comparable to FIG. 2, illustrating asecond embodiment of a gripping unit conform with the invention, and onwhich there is no part; and

[0043]FIG. 4 shows the gripping unit in FIG. 3 while machining is takingplace, seen from the side opposite to the side used in FIG. 3.

DETAILED PRESENTATION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0044] As illustrated diagrammatically in FIG. 1, a device for machiningparts conform with the invention comprises at least one gripping unit 10capable of gripping one or several parts to be machined, at least onemachine tool 12 designed to hold the gripping unit in order to doprogrammed machining of the part, and at least one loading unloadingstation capable of holding the gripping unit, in particular so that thepart can be loaded and unloaded.

[0045] In the simplest configuration diagrammatically illustrated inFIG. 1, the device comprises a single gripping unit 10, a single machinetool 12 and a single loading unloading station 14 used both for loadingthe material block to be machined and for unloading the machined part.

[0046] On the other hand, the invention also relates to a “machiningcenter” type device, including several machine tools, one or severalgripping units, one or several loading-unloading stations and at leastone device for conveying gripping units between the loading unloadingstation(s) and the different machines.

[0047] The device according to the invention may also have anyintermediate configuration between these two extreme configurations.Thus, in particular the blocks of material to be machined can be loadedand machined parts can be unloaded at different stations, usuallysimilar to each other. For simplification purposes, these two stationsare called “loading unloading stations” throughout the rest of the text.

[0048] As can also be seen in FIG. 1, the gripping unit 10 comprises apallet 16 that is in the form of a plate, preferably made of metal.

[0049] In the embodiment diagrammatically shown in FIG. 1, the plateforming the pallet 16 is a monoblock plate.

[0050] In one variant embodiment not shown, the pallet 16 may alsocomprise a lower part and an upper part free to move in rotation on thelower part, about an axis perpendicular to the face of the pallet withthe largest surface area, in this case its horizontal top face. Thelower part is then designed to be fixed in place on the plate 44 of themachine tool 12 by any appropriate means. In the case shown in which thelargest face of the pallet is horizontal, the rotation axis of the upperpart is vertical.

[0051] The pallet 16 acts as a support to gripping means 18, which areusually associated with bearing means 20. These means 18 and 20 areinterchangeable and adapted to the part to be machined.

[0052] The gripping means 18 and the bearing means 20 may in particularbe composed of vices, grips, etc. In case of bearing means 20, it mayalso consist of specific means with at least one area that bears on thepart being machined, in order to absorb and therefore to limitvibrations of the part that could be caused by machining it. In somecases, the bearing surface of the bearing means 20 may be made from asoft material or a material with good vibration absorption capacity suchas rubber.

[0053] In the embodiment illustrated in FIG. 1, the gripping means 18 ismounted on a rotary plate 22 supported by a frame 24 fixed on the plateforming the pallet 16. More precisely, the axis of rotation of the plate22 in this case is parallel to the top face (in this case horizontal) ofthe said plate. However, this arrangement is only given as an example,the nature and the possibilities of orientation of the gripping means 18being chosen as a function of the specific characteristics of the partto be machined.

[0054] Similarly, in the embodiment illustrated as an example in FIG. 1,the bearing means 20 are mounted on the plate forming the pallet 16through a rotary arm 26 capable of being pivoted about an axis parallelto the top face (in this case horizontal) of the said plate, thispivoting axis in this case being orthogonal to the axis or rotation ofthe plate 24.

[0055] The rotary plate 22 and the rotary arm 26 thus form orientationmeans for gripping means 18 and for bearing means 20. Obviously, thenumber of gripping means 18 and bearing means 20 (if any) depends on theshape and dimensions of the part to be machined.

[0056] The pallet 16 also supports the first control means 28. Thesecontrol means 28 are connected to actuators (not shown) of orientationmeans composed of the rotary plate 22 and the rotary arm 26 in theembodiment shown. They are usually also connected to actuators (notshown) of gripping means 18 and bearing means 20.

[0057] In the preferred embodiment of the invention, the first controlmeans 28 are integrated in at least one sealed box (not shown). This boxcan then protect the control means from any aggression applied to itwhen the part is being machined in the machine tool 12 (projections ofswarf, lubrication fluid, etc.). When necessary, heat dissipation means(not shown) such as a ventilation device or an air conditioning device,are provided in the box.

[0058] The actuators installed on the gripping unit 10 may be ofdifferent natures, without going outside the scope of the invention.Thus, these actuators may be controlled by a hydraulic fluid underpressure, or compressed air, a vacuum, an electrical power supply, etc.

[0059] In the embodiment shown diagrammatically in FIG. 1, the pallet 16is equipped with first connection means 32 designed to be automaticallyconnected to second complementary connection means 34 for the machinetool 12. These second connection means may for example be installed onthe plate 44 of the machine tool 12.

[0060] When they are connected, the connection means 32 and 34 firstlysupply energy to actuators installed on the gripping unit 10 from energysources available on the machine tool, and secondly control an exchangeof signals between the gripping unit and the machine tool. Thetransmission between the machine tool 12 and the gripping unit 10 willbe made through pipes and/or cables depending on the nature of theenergy used.

[0061] More precisely, signals are transmitted between the first controlmeans 28 installed on the gripping unit 10 and the second control means40 installed on the machine tool 12. For example, this transmission maybe made through cables 42, on the machine tool.

[0062] In the embodiment shown in FIG. 1, the pallet 16 is also equippedwith third connection means 36. These third connection means 36 areconnected to the first connection means 32 through lines 38 such aspipes and/or cables that transmit energies and signals. The thirdconnection means 36 are connected to the first control means 28 and tothe different actuators for example used on gripping means 18, bearingmeans 20, the rotary plate 22 and the rotary arm 26, in the embodimentshown. In this case, this transmission passes through lines 30 such aspipes or cables.

[0063] In one preferred embodiment of the invention, the gripping unit10 comprises at least one energy reservoir (not shown), for example suchas a reservoir of hydraulic fluid under pressure, a compressed airreservoir, a vacuum accumulator, an electrical power supply battery,etc. This arrangement enables the gripping means 18 and the bearingmeans 20 to continue to perform their clamping function when thegripping unit 10 is being transferred between the machine tool 12 andthe loading unloading station 14, if the said clamping function requiresa continuous energy supply.

[0064] In one variant of this preferred embodiment of the invention, thegripping unit 10 comprises onboard reservoirs for each energy used onthis unit. These reservoirs are filled when the gripping unit 10 is atthe loading unloading station. Their capacity is determined such thatthe gripping unit has sufficient energy to completely finish machiningof a part. This arrangement eliminates the need for any energytransmission through the connection means 32 and 36.

[0065] In one preferred embodiment of the invention, signals aretransmitted between the control means 28 and 40 by means of acommunication bus such as a “Profibus” or “Modbus” or other type ofindustrial field bus. This solution has the advantage that only a verylimited number of signals needs to be exchanged between the controlmeans 28 and 40. This increases reliability and reduces manufacturingcosts.

[0066] In one variant of this embodiment, communication between thecontrol means 28 and 40 passes through a communication bus using awireless link, for example such as a radio or infrared or other link.This arrangement has the advantage that no signals need to betransmitted through the connection means 32 and 36.

[0067] When this variant is combined with the presence of a reservoir onthe gripping unit 10 for each of the energies used on the gripping unit,the connection means 32 and 36 may be completely eliminated.

[0068] As mentioned above, the first control means 28 onboard grippingunit 10 in particular check the position and movements of theorientation means materialized by the rotating plate 22 and the rotatingarm 26 in FIG. 1, as a function of setpoints output from the secondcontrol means 40 installed on the machine tool.

[0069] This arrangement is advantageous, since it enables use ofsetpoints locally and independently on the gripping unit 10, without theneed for the control means 40 of the machine tool to check theorientation means. This type of control would have the disadvantage thatthe workload on the control means 40 would be increased, and manyconnections would be necessary (control signals, sensors, etc.) betweenthese control means 40 and the orientation means materialized by therotating plate 22 and the rotating arm 26. This would increase themanufacturing cost and the risk of failure.

[0070] The machine tool 12 is a high speed machining machine capable ofperforming machining operations, for example such as cutting, reaming,drilling, slicing operations, etc. It comprises the plate 44 on whichthe pallet 12 of the gripping unit 10 may be fixed. As alreadymentioned, the plate 44 comprises connection means 34 capable of beingconnected onto connection means 32 of the gripping unit 10. When theyare connected, the connection means 32 and 34 supply the energiesnecessary to the gripping unit 10 for its operation, and transmitsignals between the first control means 28 and the second control means40. In particular, the first control means 28 may receive orders fromthe second control means 40.

[0071] Conventionally, the machine tool 12 comprises at least one tool46 and means 48 capable of displacing, orienting and activating thistool.

[0072] The use of the gripping unit 10 conform with the inventionmodifies the position, orientation and possibly the grip of the partduring machining. This thus optimizes machining conditions by applyingthe best possible configuration to the relative orientation between thetool and the part, regardless of the face of the part being machined.

[0073] More precisely, modifications to the position, orientation andpossibly gripping of the part are made in the machine tool, where theyare controlled by the first control means 28 of the gripping unit 10,which receives appropriate orders from the second control means 40installed on the machine tool 12. This is very advantageous since theabove mentioned operations can thus be carried out without any action byan operator and without the need to transfer the gripping unit to theloading unloading station 14. Productivity is consequently improved.

[0074] As can also be seen in FIG. 1, the loading unloading station 14is equipped with at least one energy source capable of supplying energyto the gripping unit 10 when it is at this station.

[0075] Furthermore, the loading unloading station 14 includes thirdcontrol means 50. When the gripping unit 10 is held at the loadingunloading station 10, the third control means 50 are connected to thefirst control means 28 through connection means 32 and 36.

[0076] In practice, the third control means 50 are in the form of anoperator dialogue desk. This desk comprises at least one display means,for example such as the screen and/or lights and at least one inputmeans, for example such as a keyboard and/or push buttons.

[0077] As has already been mentioned, the machining device may alsocomprise one or several conveying means capable of routing each grippingunit 10 between the machine tool 12 and the loading unloading station14.

[0078] Any mechanical parts can be machined using a machining devicelike that described above, using a machining process that will now bedescribed.

[0079] Firstly, this process comprises a design phase during which aprogrammer defines the operational machining process. More precisely,the programmer defines the various orientations that must be applied tothe block of material to be machined, and the various machiningsequences corresponding to each of these orientations. In particular,these machining sequences include changes to the position andorientation of the tool, its displacements and tool changes, if any. Thedefinition of successive orientations of the block of material to bemachined consists of making changes to the orientation and/or grippingof the said block.

[0080] If a series of identical parts has to be produced, the designphase is common to all parts.

[0081] The machining process then comprises a manufacturing phase. Whenseveral identical parts have to be made, this manufacturing phase isrepeated for each part.

[0082] During a first step in the machining process phase, a grippingunit 10 is brought to the loading unloading station 14.

[0083] An operator then puts gripping means 18, and possibly bearingmeans 20 adapted to the part to be machined such as one or severalvices, grips, etc., into place on this gripping unit. These differentgripping and bearing means are inter-changeable and can therefore bereplaced quickly as a function of the type of part to be machined, suchthat this operation does not reduce productivity.

[0084] In a first embodiment, this operation is done entirely manually.The operator unlocks the gripping means already in place and removesthem from their support by a mechanical action. He then puts thegripping means adapted to the part to be machined into place, and thenlocks them in position by a new mechanical action.

[0085] In another embodiment, the operator carries out unlocking andthen locking operations on the gripping means by acting on input meanson the desk forming the third control means 50, so as to formulate arequest on the first control means 28. The control means 28 then controlthe actuators to perform the required operations.

[0086] The operator then positions a block of rough material from whichthe part to be made has to be machined, in the gripping unit 10. Theposition and orientation of this block correspond to the position andorientation that were defined previously during the design phase.

[0087] Consequently, an appropriate support may be placed on a fixedpart of the gripping unit 10, such as the pallet 16, in order toposition the block of material and hold it in place in this positionuntil it is gripped by the gripping means 18. The operator then acts onthe desk input means forming the third control means 50, in order tomake a query to the first control means 28 to actuate the gripping means18 and possibly the bearing means 20. The block of material can thus beclamped in the required position and orientation.

[0088] The gripping unit is then removed from the loading unloadingstation, after the energy supply line and the signal transmission linehave been disconnected.

[0089] Depending on the scheduling and planning of workshop tasks, thegripping unit 10 may be brought either into a temporary storage area, orbrought directly into the appropriate machine tool 12.

[0090] When the gripping unit 10 reaches the plate 44 of the machinetool 12, the pallet 16 is placed on the plate 44 and is fixed to it. Theconnection means 32 and 34 are then connected to make appropriateconnections for energies and signals.

[0091] The part is then machined following sequences previously definedduring the design phase. More precisely, the sequences relative to eachorientation of the part are executed in turn, each sequence beingfollowed by a change to the part orientation achieved by taking actionon the orientation means and/or on the gripping means. These variousoperations are controlled by control means 28 of the gripping unit, inresponse to orders originating from control means 40 of the machine tool12. Thus, the part can be completely machined fully automaticallywithout returning the gripping unit to the loading unloading station,under optimum cutting and swarf removal conditions.

[0092] Once machining is finished, the gripping unit 10 is disconnectedand removed from the machine tool 12, and is then transferred either toa waiting position, or to a loading unloading station. The loadingunloading station may be but is not necessarily coincident with thestation 14 assigned to loading the block of material to be machined,depending on the configuration of the workshop.

[0093] When the gripping unit is at the loading unloading station, anoperator acts on the desk input means that materialize the third controlmeans 50. These means then formulate a request so that the first controlmeans 28 activate the gripping means 18 and possibly the bearing means20, to release the part.

[0094] We will now describe a first embodiment of the gripping unitaccording to the invention, with reference to FIG. 2.

[0095] In this embodiment, the gripping unit 10 is arranged to machine ablock of material B in an elongated and approximately parallelepipedshape. In particular, this block B may be an aluminum block.

[0096] As described above, the gripping unit 10 comprises a pallet 16,of which only the top rotating part is shown. In the example described,the rotating part of the pallet 16 may rotate by 285° about a verticalaxis.

[0097] The pallet 16 supports the fixed frame 24 a of a rotating plate22 a equipped with gripping means, in this case consisting of a vice 18a. Furthermore, a second vice 18 b is installed on a second rotatingplate 22 b supported on a mobile frame 24 b. This mobile frame 24 b isinstalled on the pallet 16 so that it can be moved towards the fixedframe 24 a and moved away from it, along a direction passing through anaxis common to the two rotating plates 22 a and 22 b, throughtranslation means 52. The pallet 16 also supports a rotating arm 26 onwhich a grip 20 is installed materializing the bearing means placedbetween frames 24 a and 24 b. In the example described, the rotatingplates 22 a and 22 b are of the “Reiseler” AWU355 type with encoders andthere are 360 000 possible positions on one turn.

[0098] In this case, the first control means are located in three boxes28 a, 28 b and 28 c. The first box 28 a may for example be assigned tothe energy supply and to filters. The second box 28 b in particularcontains a programmable logic controller, an interface with a “Profibus”type communication bus, and regulation cards. For example, the third box28 c is a hydropneumatic box particularly containing solenoid valves.

[0099] The gripping unit 10 in FIG. 2 communicates with the controlmeans 40 of the machine tool 12 (FIG. 1) through a “Profibus” typecommunication network.

[0100] The translation means 52 can be used to adjust the relativeposition of the rotating plate 22 b with respect to the rotating plate22 a, so that the block of material B in which the part is machined isfirmly gripped between vices 18 a and 18 b.

[0101] When the gripping unit that has been described with reference toFIG. 2 is transferred to the loading unloading station 14, an operatorputs the vices 18 a and 18 b into place on the rotating plates 22 a and22 b and the clamp 20 into place on the rotating arm 26.

[0102] The operator then adjusts the position of frame 24 b supportingthe vice 18 b in translation, such that the distance between the vices18 a and 18 b is compatible with the length of the block of material Bto be machined. This adjustment is made by adjusting the control means50 of the loading unloading station 14 on the desk, the said desk beingconnected to the logic controller contained in the box 28 b on thegripping unit.

[0103] The operator also adjusts the positions of the plates 22 a and 22b in rotation, and consequently the position of the vices 18 a and 18 bso that the block of material B can be placed between the said vicessuch that they are correctly aligned and do not create any torsion whenthe block of material is then clamped in the vices.

[0104] The operator then puts a support (not shown) into place on thepallet 16. He then has the block of material B on the said support andpositions it such that its ends are placed between the jaws of the vices18 a and 18 b. By acting on the desk materializing the control means 50,the operator activates the jaws of the vices in order to clamp the blockof material B. This block of material is then held in position by vices18 a and 18 b and the operator can remove the previously mentionedsupport.

[0105] The gripping unit 10 is then conveyed to the machine tool 12. Thegripping unit 10 may also be transferred to a temporary storage areawhile waiting to be routed to the machine tool, depending on thescheduling of tasks in the workshop.

[0106] In the machine tool, the block of material to be machined ispresented in front of tool 46 in a position to give the best cutting andswarf evacuation conditions. Consequently, the control means 40 of themachine tool 12 can send a change position or change orientation orderfor the block of material B to the logic controller contained in the box28 b, through the “Profibus” network.

[0107] This position or orientation change may be obtained by ordering arotation of the top part of the pallet 16 and/or simultaneous rotationof plates 22 a and 22 b. These plates must be activated so as to avoidgenerating torsion on the block of material. Consequently, a firstsolution consists of driving the two plates in rotation synchronously.Another solution consists of only applying a motor drive to one of theplates, the second plate being free in rotation.

[0108] As already mentioned, a tension force may be applied to the blockof material B being machined. This force is then applied along thelongitudinal axis of the said block, by taking action on thedisplacement device 52. The resonant frequency of the material block Bis thus modified so as to limit the vibrations.

[0109] Once the position has been changed, the logic controllercontained in the box 28 b sends a message to the control means 40 of themachine tool 12 through the “Profibus” network in order to inform itthat this operation has been completed. The control means 40 can thencontrol execution of the following machining steps.

[0110] In this way, the part held in place by vices 18 a and 18 b can bemachined on all its faces. Thus, the end faces of the part,approximately perpendicular to the axis of rotation common to plates 22a and 22 b, may be machined provided that tabs are left between the saidpart and the portions of the material block clamped between the jaws ofvices 18 a and 18 b. These tabs may be sawn after the part isdisassembled at the loading unloading station. They may also be cut byan appropriate tool on the machine tool, the finished part then beingpicked up by the clamp 20 located at the end of the rotating arm 26. Thefinished part is then held in position by clamp 20 and residues from theends of the block B are held in position by clamps 18 a and 18 b.

[0111] Once machining is finished, the gripping unit is taken out of themachine tool 12 and is transferred to the initial loading unloadingstation or to another similar station. An operator then controls releaseof the part using gripping means 18 a, 18 b or 20. Consequently, hemakes a request to the logic controller contained in the box 28 b, bytaking action on the desk that materializes the control means 50.

[0112] We will now describe a second embodiment of the gripping unitaccording to the invention, with reference to FIGS. 3 and 4.

[0113] In this embodiment, the gripping unit 10′ is arranged to machinea block of material B′ in the form of an approximately flat plate, tomake a part such as a frame for an aircraft windshield.

[0114] As illustrated particularly in FIG. 3, the gripping unit 10′comprises a pallet 16 supporting the frame 24 of a rotating plate 22 onwhich gripping means 18′ are installed. The pallet 16 also supports twogripping arms 26 a and 26 b on which clamps 20 a and 20 b are installed,and three boxes 28 a, 28 b and 28 c in which the control means arefitted, in the same way as in the embodiment described above withreference to FIG. 2. As before, the gripping unit 10′ communicates withthe control means 40 of the machine tool 12 through a “Profibus”network.

[0115] The gripping means 18′ are in the form of eight pins D1 to D8distributed on a circle centered on the axis of the rotating plate 22,to project on the front face of the said plate. More precisely, thediametrically opposite pins D1 and D2 are rods fixed to the rotatingplate 22. The diametrically opposite pins D3 and D4 are gripping pinsthat can move parallel to the axis of the rotating plate 22. Each of thepins comprises an expansion mandrel installed on a jack rod, to achievethis. Finally, pins D5 to D8 are fixed gripping jacks, in other wordsthey each comprise an expansion mandrel installed on a rod fixed to therotating plate 22.

[0116] Eight holes are drilled in the central part of the plate formingthe block of material B′ to be machined, arranged in the same way as theeight pins D1 to D8.

[0117] When the gripping unit 10′ is at the loading unloading station14, an operator puts the pins D1 to D8 forming the gripping means 18′into place on the rotating plate 22. He also puts the clamps 20 a and 20b into place on the rotating arms 26 a and 26 b.

[0118] The operator then puts the block of material B′ into position onthe gripping means 18′, by inserting pins D1 to D8 into the holes formedin the said block. The fixed pins D1 and D2 then act as guides.

[0119] The operator then controls expansion of the mandrels installed onpins D3 and D4 in the corresponding holes of the block of material B′,in order to hold this block in position. He does this on the deskmaterializing the control means 50 of the loading unloading station 14,the said desk being connected to the control means of the gripping units10′.

[0120] The operator then controls withdrawal of the two jacks installedon pins D3 and D4, to force the material block B′ into contact with therotating plate 22, to give better support. Advantageously, sensorsdetect that the block of material is actually in firm contact with theplate. The mandrels of the four other pins D5 to D8 are then expanded intheir corresponding holes in order to complete gripping of the materialblock B′.

[0121] The operator then controls conveying of the gripping unit 10′towards the machine tool or to a temporary storage area, as wasdescribed above with reference to FIG. 2.

[0122] In the machine tool, the part is presented in front of tool 46 ina position used to obtain the best cutting and swarf evacuationconditions. As in the previous embodiment, this is achieved by thecontrol means 40 of the machine tool 12 sending an order to changeposition or change orientation of the material block to the logiccontroller contained in the box 28 b, through the “Profibus” network.The position or orientation change may be made by controlling rotationof the top part of the pallet 16 and/or rotating the plate 22 on whichpins D1 to D8 are installed. Action can also be taken on the rotatingarms 26 a and 26 b, in order to obtain a good grip of the block ofmaterial to minimize vibrations.

[0123] Once the position and/or orientation change has been made, thelogic controller contained in the box 28 b sends a message to thecontrol means 40 of the machine tool 12, through the “Profibus” networkin order to inform the machine tool that this operation is complete. Thecontrol means 40 of the machine tool 12 can then control the actualmachining steps.

[0124] A first step of the machining preferably consists of making a setof tenons T′ around the periphery of the plate forming the block ofmaterial B′ to be machined. These tenons T′ are designed to enable abetter grip of the said block by clamps 20 a and 20 b later on. Whilethe tenons T′ are being machined, the block of material B′ is held onlyby the gripping means 18′.

[0125] The block of material B′ can then be machined on all its faces,and it can be gripped by pins D1 to D8 and by clamps 20 a and 20 b.

[0126] Tabs of material P are left in place between the centralunmachined part fixed to the plate 22 and the part itself as shown inFIG. 4, so that the block B′ can be oriented in rotation for as long aspossible using the rotating plate 22 and to minimize deformations duringmachining. These tabs P may be cut using an appropriate tool, on themachine tool 12, once machining is finished. The tabs P can also be cutlater, once the part has been removed from the gripping unit.

[0127] Similarly, the tabs P′ are also left between the tenons T′ andthe part, so that the part can be held in place by clamps 20 a. and 20b. These tabs P′ are cut after the part has been removed from thegripping unit.

[0128] When machining is finished, the gripping unit is taken out of themachine tool and is conveyed to the first loading unloading station orto another station similar to the first loading unloading station. Anoperator then controls releasing the part using the gripping means 18′,20 a and 20 b. He does this by making a request to the logic controllerinstalled in box 28 b, by taking action on the desk that materializesthe control means 50. Advantageously, the above mentioned logiccontroller controls ejectors that facilitate evacuation of the centralunmachined part of block B′, held in place by gripping means 18′.

1. Gripping unit capable of being transferred between at least onemachine tool and at least one loading unloading station, to enableautomated machining of at least one part, the gripping unit comprising apallet and gripping means for gripping the said part, mounted on thepallet and characterized in that it also comprises orientation means bywhich the gripping means are mounted on the pallet, control meanscapable of activating the orientation means in response to controlsignals output from the machine tool, and bearing means mounted on thepallet through other orientation means.
 2. Gripping unit according toclaim 1, in which the control means are also capable of activating thegripping means.
 3. Gripping unit according to claim 1, comprising alsoat least one frame fixed on the pallet and a rotating plate mounted onthe frame and forming the orientation means, the gripping means beinginstalled on the rotating plate.
 4. Gripping unit according to claim 1,in which the bearing means comprise at least one surface that can beapplied onto the part, the said surface being made of a material capableof absorbing vibrations.
 5. Gripping unit according to claim 1, in whichthe said other orientation means comprise a rotating arm mounted on thepallet.
 6. Gripping unit according to claim 1, in which the grippingmeans are interchangeable.
 7. Gripping unit according to claim 1, inwhich the pallet comprises a part free to move in rotation about an axisperpendicular to a face of the pallet with the largest surface area, thegripping means being mounted on the said mobile part.
 8. Gripping unitaccording to claim 1, also comprising first connection means that can beautomatically connected to the second connection means mounted on themachine tool when the gripping unit is fitted in the machine tool. 9.Gripping unit according to claim 8, also comprising third connectionmeans, connected firstly to the first connection means and secondly tothe orientation means and to the control means.
 10. Gripping unitaccording to claim 1, in which the control means are connected to acommunication bus capable of transmitting the control signals. 11.Gripping unit according to claim 10, in which the communication bus is awireless communication bus.
 12. Gripping unit according to claim 1, alsocomprising at least one onboard energy reserve.
 13. Gripping unitaccording to claim 12, in which the energy reserve is capable ofsupplying a quantity of energy necessary for complete machining of anarbitrary part on the machine tool.
 14. Gripping unit according to claim1, in which the gripping unit means are capable of applying a tensionforce onto the part, to modify its natural frequency.
 15. Gripping unitaccording to claim 14, in which means of detecting vibrations areinstalled on at least one of the gripping means.
 16. Gripping unitaccording to claim 15, in which the signals output by the vibrationdetection means are transmitted to the control means that regulate thetension force exerted on the part in order to minimize the saidvibrations.
 17. Gripping unit according to claim 1, in which the controlmeans are placed in at least one sealed box.
 18. Gripping unit accordingto claim 17, in which the sealed box is provided with heat dissipationmeans.
 19. Part machining device, comprising at least one gripping unitcapable of being transferred between at least one machine tool and atleast one loading unloading station, to enable automated machining of atleast one part, the gripping unit comprising a pallet and means ofgripping the said part mounted on the pallet, in which the said unitalso comprises orientation means by which the gripping means are mountedon the pallet, control means capable of selecting the orientation meansin response to control signals from the machine tool, and bearing meansmounted on the pallet by other orientation means, the machining devicealso comprising at least one machine tool capable of holding thegripping unit, at least one loading unloading station capable of holdingthe gripping unit and means capable of supplying energy to the grippingunit, in which each machine tool also comprises second control meanscapable of sending the said control signals and signal transmissionmeans are provided to transmit the said control signals between thegripping unit control means and the second control means, when thegripping unit is held on the machine tool.
 20. Machining deviceaccording to claim 19, in which the loading unloading station includesthird control means capable of sending control signals for the grippingmeans, and the transmission means are also capable of transmittingcontrol signals for the gripping means when the gripping unit is held atthe loading unloading station.
 21. Machining device according to claim20, in which the third control means comprise at least one display meansand at least one input means.
 22. Machining device according to claim19, the gripping unit also comprising first connection means capable ofbeing automatically connected to the second connection means mounted onthe machine tool when the gripping unit is held in the machine tool, andin which the said transmission means also comprise fourth connectionmeans mounted on the loading unloading station, the said first andfourth connection means being automatically connected to each other whenthe gripping unit is held on the loading unloading station. 23.Machining device according to claim 19, in which the means capable ofsupplying energy to the gripping unit comprise at least one energysource installed on the machine tool and energy transmission means totransmit energy between the said energy source and the control means ofthe gripping unit.
 24. Machining device according to claim 23, in whichthe gripping unit also comprises first connection means capable of beingautomatically connected to the second connection means installed on themachine tool when the gripping unit is fitted in the machine tool, andin which the first and second connection means also form part of theenergy transmission means.
 25. Machining device according to claim 19,in which the machine tool is a high speed machining machine. 26.Machining device according to claim 19, in which at least one conveyingmeans is provided to transfer the gripping unit between the machine tooland the loading unloading station.
 27. Process for machining parts usinga part machining device, comprising at least one gripping unit capableof being transferred between at least one machine tool and at least oneloading unloading station, to enable automated machining of at least onepart, the gripping unit comprising a pallet and means of gripping thesaid part mounted on the pallet, in which the said unit also comprisesorientation means, through which the gripping means are mounted on thepallet, control means capable of actuating orientation means in responseto control signals from the machine tool, and bearing means mounted onthe pallet through other orientation means, the machining device alsocomprising at least one machine tool capable of holding the grippingunit, at least one loading unloading station capable of holding thegripping unit and means capable of supplying energy to the grippingunit, in which each machine tool also comprises second control meanscapable of sending the said control signals and signal transmissionmeans are provided to transmit the said control signals between thegripping unit control means and the second control means, when thegripping unit is held on the machine tool, the said process comprisingthe following phases: a design phase consisting of defining successiveorientations of a part in the machine tool and machining sequencesspecific to each of these orientations: a manufacturing phase comprisingthe following steps: placement of the gripping unit at the loadingunloading station; placement of gripping means on the gripping unit;positioning of a block of material to be machined on the gripping unitand clamping of the said block by the gripping means; transfer andplacement of the gripping unit on the machine tool; orientation of thesaid block in a first of the predefined orientations, when acted upon byorientation means controlled by the control means of the gripping unit,at the request of the second control means; execution of machiningsequences corresponding to this first position; repetition of the blockorientation and machining sequence execution steps as many times asnecessary, in accordance with the design phase, until the part iscompleted; transfer of the gripping unit to the loading unloadingstation; loosening and unloading the part.
 28. Process according toclaim 27, in which the design phase is common to the machining ofseveral identical parts and the manufacturing phase is repeated whileeach part is machined.